Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Kinesiology

Faculty/School

Faculty of Science

First Advisor

Mark Babcock

Advisor Role

Thesis Supervisor

Abstract

Exercise induced arterial hypoxemia (EIAH), expiratory flow limitation (EFL) and exercise induced diaphragm fatigue (EIDF) are examples of how the pulmonary system limits endurance exercise. The differences in the female anatomy and hormone fluctuations have been reported to cause differences in the occurrence of EIAH and EFL in males and females. EIDF has been reported to occur in males, but to date no investigations have reported the occurrence of EIDF in females. Therefore the purpose of this study was to determine the occurrence of exercise induced diaphragm fatigue (EIDF) in females identified by significant reductions in transdiaphramatic pressure (Pdi) post exercise in response to supramaximal bilateral phrenic nerve stimulation.

Ten females 20 (± 0.37) years old completed exercise at 75 and 95% V02max to volitional fatigue on 2 separate days, on approximately day 7 (± 2 days) of their menstrual cycle. Bilateral phrenic nerve stimulation in combination with balloon tipped catheters, used to measure esophageal and gastric pressure, were used to provide an objective measurement of trans-diaphragmatic pressure. BPNS was performed at 1,10,20,50, and 100 Hz prior to exercise, immediately after exercise, 30, and 60 minutes after exercise.

Post exercise there were no significant reductions in Pdi after the 75% V02max exercise condition; however, in the 95% V02max exercise condition Pdi was significantly reduced with 1 and 50 Hz stimulation. Recovery from fatigue occurred within approximately 30 minutes after exercise. This study objectively reported the occurrence of EIDF in females exercising at 95% V02max.

Convocation Year

2008

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